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Recent global warming is often labeled as « abnormal » or « without precedent ». It actually had equivalents in 750, 1000, 1400 and 1750 and the two-century long period around 1000AD was warmer and longer than generally recognized… at least in Northern Europe Medieval climatic optimum Grudd, 2008 Grudd, 2002

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Time variations of the mean period of the MJO wave packet (MJO1 index), taken between 30–60 days (a) and 50–80 days (b). The difference between the two is compared to sunspot number (c) and mean quadratic variation of Z component in the Alibag magnetic observatory (d). (4 year running means) The Madden-Julian oscillation 2

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Tinsley et Heelis, 1993 Accumulation of electric charges at the boundaries of layered clouds results from vertical current density Jz from the ionosphere to the surface. Charges attach to droplets and aerosols and alter cloud microphysics.

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Global warming ? Yes, over the past 150 years, but very irregular… Not without precedent in the past two thousand years … Complex and multiple sources, uncertainties insufficiently taken into account in models… Conclusion (2):

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Conclusion (3): Growing evidence along several lines for significant influence of decadal to multi-decadal variations in solar activity on a number of climate related features, with an amplitude well beyond that expected for 1/1000 changes in total solar irradiance. Some of the effects we find have a relative amplitude in excess of 30% of the original signals. Mechanism likely involve cosmic rays and/or vertical currents in ionosphere and atmosphere, and clouds.

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How expertise is gathered and advice built (the « consensus »): a risk for « anti-science » backfiring Other important problems running the risk of being considered as secundary : - the quest for drinking water - management of urban waste - hunger in the world … Geoscientists can be sources of solutions to several of these problems… How expertise is gathered and advice built (the « consensus »): a risk for « anti-science » backfiring Other important problems running the risk of being considered as secundary : - the quest for drinking water - management of urban waste - hunger in the world … Geoscientists can be sources of solutions to several of these problems… Conclusion (4) and discussion: